There are many different types of objects, liquids and substances that glow when exposed to black light. Generally, these liquids have molecules with rigid structures and delocalized electrons because these properties usually lend themselves to the reaction of glowing under a black light. Some examples of liquids that glow under a black light are petroleum jelly, tonic water, water with vitamins in it, antifreeze and even some bodily fluids.
When fluorescent substances are exposed to a black light, they glow. This is because they absorb the ultraviolet light that emits from the black light device and re-emit it. A slight modification in energy occurs, however, which makes the emitted light visible to the human eye. Because of this effect, certain substances appear to glow. Some animals even glow under a black light.
Other types of liquids that glow under a black light include chlorophyll, laundry detergent and some types of cleaners. Tooth whiteners also often glow under a black light. Because these materials are composed of different things, but have a similar effect on the energy they absorb from the black light, they do not all glow in precisely the same way. In fact, many substances glow in different colors from one another when exposed to a black light.